In the Wire Association International, Inc. Nonferrous Wire Handbook Volume 3, there is a chapter (Page 564) titled "Measurement of Oxide and Sulfide Films on Copper Rod and Wire" It was written by Dr. Horace Pops and is 6 pages long. Within that chapter is a section titled "Determination of Film Thickness" and it describes how one can determine the thickness of cuprous oxide, cupric oxide, cuprous sulfide and so on.

The method starts with "Voltage versus Time" plots obtained by an electrolytic reduction procedure and this is too complex to be included in this Forum. It also includes sketches. An equation is used to calculate the thickness, again too complicated to be placed in the Forums. This equation employs Faradays but as I am sure you know; 1 coulomb = 1.03642686 × 10-5 Faradays. The thickness is in centimeters but as we already discussed an ångström or angstrom (symbol Å) is an internationally recognized non-SI unit of length equal to 0.1 nanometer or 1×10−10 meters.